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Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-05) exists of draft-fleischhauer-ipv4-addr-saving-03 -- Obsolete informational reference (is this intentional?): RFC 6555 (Obsoleted by RFC 8305) Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group S. Perreault 3 Internet-Draft Jive Communications 4 Intended status: Informational T. Tsou 5 Expires: September 26, 2015 Huawei Technologies (USA) 6 C. Zhou 7 Huawei Technologies 8 P. Fan 9 China Mobile 10 March 25, 2015 12 Gap Analysis for IPv4 Sunset 13 draft-ietf-sunset4-gapanalysis-06 15 Abstract 17 Sunsetting IPv4 refers to the process of turning off IPv4 18 definitively. It can be seen as the final phase of the migration to 19 IPv6. This memo enumerates difficulties arising when sunsetting 20 IPv4, and identifies the gaps requiring additional work. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at http://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on September 26, 2015. 39 Copyright Notice 41 Copyright (c) 2015 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (http://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Related Work . . . . . . . . . . . . . . . . . . . . . . . . 3 58 3. Remotely Disabling IPv4 . . . . . . . . . . . . . . . . . . . 4 59 3.1. Indicating that IPv4 connectivity is unavailable . . . . 4 60 3.2. Disabling IPv4 in the LAN . . . . . . . . . . . . . . . . 4 61 4. Client Connection Establishment Behavior . . . . . . . . . . 4 62 5. Disabling IPv4 in Operating System and Applications . . . . . 5 63 6. On-Demand Provisioning of IPv4 Addresses . . . . . . . . . . 5 64 7. IPv4 Address Literals . . . . . . . . . . . . . . . . . . . . 6 65 8. Managing Router Identifiers . . . . . . . . . . . . . . . . . 6 66 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 67 10. Security Considerations . . . . . . . . . . . . . . . . . . . 7 68 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 7 69 12. Informative References . . . . . . . . . . . . . . . . . . . 7 70 Appendix A. Solution Ideas . . . . . . . . . . . . . . . . . . . 9 71 A.1. Remotely Disabling IPv4 . . . . . . . . . . . . . . . . . 9 72 A.1.1. Indicating that IPv4 connectivity is unavailable . . 9 73 A.1.2. Disabling IPv4 in the LAN . . . . . . . . . . . . . . 9 74 A.2. Client Connection Establishment Behavior . . . . . . . . 10 75 A.3. Disabling IPv4 in Operating System and Applications . . . 10 76 A.4. On-Demand Provisioning of IPv4 Addresses . . . . . . . . 10 77 A.5. Managing Router Identifiers . . . . . . . . . . . . . . . 10 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 80 1. Introduction 82 The final phase of the migration to IPv6 is the sunset of IPv4, that 83 is turning off IPv4 definitively on the attached networks and on the 84 upstream networks. 86 Some current implementation behavior makes it hard to sunset IPv4. 87 Additionally, some new features could be added to IPv4 to make its 88 sunsetting easier. This document analyzes the current situation and 89 proposes new work in this area. 91 The decision about when to turn off IPv4 is out of scope. This 92 document merely attempts to enumerate the issues one might encounter 93 if that decision is made. 95 2. Related Work 97 [RFC3789], [RFC3790],[RFC3791], [RFC3792], [RFC3793], [RFC3794], 98 [RFC3795] and [RFC3796] contain surveys of IETF protocols with their 99 IPv4 dependencies. 101 Additionally, although reviews in RFCs 3789-3796 ensured that IETF 102 standards then in use could support IPv6, no IETF-wide effort has 103 been undertaken to ensure that the issues identified in those drafts 104 are all addressed, nor to ensure that standards written after RFC3100 105 (where the previous review efforts stopped) function properly on 106 IPv6-only networks. 108 The IETF needs to ensure that existing standards and protocols have 109 been actively reviewed, and any parity gaps either identified so that 110 they can be fixed, or documented as unnecessary to address because it 111 is unused or superseded by other features. 113 First, the IETF must review RFCs 3789-3796 to ensure that any gaps in 114 specifications identified in these documents and still in active use 115 have been updated as necessary to enable operation in IPv6-only 116 environments (or if no longer in use, are declared historic). 118 Second, the IETF must review documents written after the existing 119 review stopped (according to RFC 3790, this review stopped with 120 approximately RFC 3100) to identify specifications where IPv6-only 121 operation is not possible, and update them as necessary and 122 appropriate, or document why an identified gap is not an issue i.e. 123 not necessary for functional parity with IPv4. 125 This document does not recommend excluding Informational and BCP RFCs 126 as the previous effort did, due to changes in the way that these 127 documents are used and their relative importance in the RFC Series. 128 Instead, any documents that are still active (i.e. not declared 129 historic or obsolete) and the product of IETF consensus (i.e. not a 130 product of the ISE Series) should be included. In addition, the 131 reviews undertaken by RFCs 3789-3796 were looking for "IPv4 132 dependency" or "usage of IPv4 addresses in standards". This document 133 recommends a slightly more specific set of criteria for review: 134 review should include consideration of whether the specification can 135 operate in an environment without IPv4. Reviews should include 136 guidance on the use of 32-bit identifiers that are commonly populated 137 by IPv4 addresses. Reviews should include consideration of protocols 138 on which specifications depend or interact, to identify indirect 139 dependencies on IPv4. Finally, reviews should consider how to 140 migrate from an IPv4 environment to an IPv6 environment. 142 3. Remotely Disabling IPv4 144 3.1. Indicating that IPv4 connectivity is unavailable 146 PROBLEM 1: When an IPv4 node boots and requests an IPv4 address 147 (e.g., using DHCP), it typically interprets the absence 148 of a response as a failure condition even when it is not. 150 PROBLEM 2: Home router devices often identify themselves as default 151 routers in DHCP responses that they send to requests 152 coming from the LAN, even in the absence of IPv4 153 connectivity on the WAN. 155 3.2. Disabling IPv4 in the LAN 157 PROBLEM 3: IPv4-enabled hosts inside an IPv6-only LAN can auto- 158 configure IPv4 addresses [RFC3927] and enable various 159 protocols over IPv4 such as mDNS 160 [I-D.cheshire-dnsext-multicastdns] and LLMNR [RFC4795]. 161 This can be undesirable for operational or security 162 reasons, since in the absence of IPv4, no monitoring or 163 logging of IPv4 will be in place. 165 PROBLEM 4: IPv4 can be completely disabled on a link by filtering it 166 on the L2 switching device. However, this may not be 167 possible in all cases or may be too complex to deploy. 168 For example, an ISP is often not able to control the L2 169 switching device in the subscriber home network. 171 PROBLEM 5: A host with only Link-Local IPv4 addresses will "ARP for 172 everything", as described in Section 2.6.2 of [RFC3927]. 173 Applications running on such a host connected to an 174 IPv6-only network will believe that IPv4 connectivity is 175 available, resulting in various bad or sub-optimal 176 behavior patterns. See 177 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp] for further 178 analysis. 180 Some of these problems were described in [RFC2563], which 181 standardized a DHCP option to disable IPv4 address auto- 182 configuration. However, using this option requires running an IPv4 183 DHCP server, which is contrary to the goal of IPv4 sunsetting. 185 4. Client Connection Establishment Behavior 187 PROBLEM 6: Happy Eyeballs [RFC6555] refers to multiple approaches to 188 dual-stack client implementations that try to reduce 189 connection setup delays by trying both IPv4 and IPv6 190 paths simultaneously. Some implementations introduce 191 delays which provide an advantage to IPv6, while others 192 do not [Huston2012]. The latter will pick the fastest 193 path, no matter whether it is over IPv4 or IPv6, 194 directing more traffic over IPv4 than the other kind of 195 implementations. This can prove problematic in the 196 context of IPv4 sunsetting, especially for Carrier-Grade 197 NAT phasing out because CGN does not add significant 198 latency that would make the IPv6 path more preferable. 199 Traffic will therefore continue using the CGN path unless 200 other network conditions change. 202 PROBLEM 7: getaddrinfo() [RFC3493] sends DNS queries for both A and 203 AAAA records regardless of the state of IPv4 or IPv6 204 availability. The AI_ADDRCONFIG flag can be used to 205 change this behavior, but it relies on programmers using 206 the getaddrinfo() function to always pass this flag to 207 the function. The current situation is that in an 208 IPv6-only environment, many useless A queries are made. 210 5. Disabling IPv4 in Operating System and Applications 212 It is possible to completely remove IPv4 support from an operating 213 system as has been shown by the work of Bjoern Zeeb on FreeBSD. 214 [Zeeb] Removing IPv4 support in the kernel revealed many IPv4 215 dependencies in libraries and applications. 217 PROBLEM 8: Completely disabling IPv4 at runtime often reveals 218 implementation bugs. Hard-coded dependencies on IPv4 219 abound, such as on the 127.0.0.1 address assigned to the 220 loopback interface. It is therefore often operationally 221 impossible to completely disable IPv4 on individual 222 nodes. 224 PROBLEM 9: In an IPv6-only world, legacy IPv4 code in operating 225 systems and applications incurs a maintenance overhead 226 and can present security risks. 228 6. On-Demand Provisioning of IPv4 Addresses 230 As IPv6 usage climbs, the usefulness of IPv4 addresses to subscribers 231 will become smaller. This could be exploited by an ISP to save IPv4 232 addresses by provisioning them on-demand to subscribers and 233 reclaiming them when they are no longer used. This idea is described 234 in [I-D.fleischhauer-ipv4-addr-saving] and [BBF.TR242] for the 235 context of PPP sessions. In these scenarios, the home router is 236 responsible for requesting and releasing IPv4 addresses, based on 237 snooping the traffic generated by the hosts in the LAN, which are 238 still dual-stack and unaware that their traffic is being snooped. 240 PROBLEM 10: Dual-stack hosts that implement Happy-Eyeballs [RFC6555] 241 will generate both IPv4 and IPv6 traffic even if the 242 algorithm end up chooosing IPv6. This means that an IPv4 243 address will always be requested by the home router, 244 which defeats the purpose of on-demand provisioning. 246 PROBLEM 11: Many operating systems periodically perform some kind of 247 network connectivity check as long as an interface is up. 248 Similarly, applications often send keep-alive traffic 249 continuously. This permanent "background noise" will 250 prevent an IPv4 address from being released by the home 251 router. 253 PROBLEM 12: Hosts in the LAN have no knowledge that IPv4 is available 254 to them on-demand only. If they had explicit knowledge 255 of this fact, they could tune their behaviour so as to be 256 more conservative in their use of IPv4. 258 PROBLEM 13: This mechanism is only being proposed for PPP even though 259 it could apply to other provisioning protocols (e.g., 260 DHCP). 262 7. IPv4 Address Literals 264 IPv4 addresses are often used as resource locators. For example, it 265 is common to encounter URLs containing IPv4 address literals on web 266 sites [I-D.wing-behave-http-ip-address-literals]. IPv4 address 267 literals may be published on media other than web sites, and may 268 appear in various forms other than URLs. For the operating systems 269 which exhibit the behavior described in 270 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp], this also means an 271 increase in the broadcast ARP traffic, which may be undesirable. 273 PROBLEM 14: IPv6-only hosts are unable to access resources identified 274 by IPv4 address literals. 276 8. Managing Router Identifiers 278 IPv4 addresses are often conventionally chosen to number a router ID, 279 which is used to identify a system running a specific protocol. The 280 common practice of tying an ID to an IPv4 address gives much 281 operational convenience. A human-readable ID is easy for network 282 operators to deal with, and it can be auto-configured, saving the 283 work of planning and assignment. It is also helpful to quickly 284 perform diagnosis and troubleshooting, and easy to identify the 285 availability and location of the identified router. 287 PROBLEM 15: In an IPv6 only network, there is no IP address that can 288 be directly used to number a router ID. IDs have to be 289 planned individually to meet the uniqueness requirement. 290 Tying the ID directly to an IP address which yields 291 human-friendly, auto-configured ID that helps with 292 troubleshooting is not possible. 294 9. IANA Considerations 296 None. 298 10. Security Considerations 300 It is believed that none of the problems identified in this draft are 301 security issues. 303 11. Acknowledgements 305 Thanks in particular to Andrew Yourtchenko, Lee Howard, Nejc 306 Skoberne, and Wes George for their thorough reviews and comments. 308 Special thanks to Marc Blanchet who was the driving force behind this 309 work and to Jean-Philippe Dionne who helped with the initial version 310 of this document. 312 12. Informative References 314 [BBF.TR242] 315 Broadband Forum, "TR-242: IPv6 Transition Mechanisms for 316 Broadband Networks", August 2012. 318 [Huston2012] 319 Huston, G. and G. Michaelson, "RIPE 64: Analysing Dual 320 Stack Behaviour and IPv6 Quality", April 2012. 322 [I-D.cheshire-dnsext-multicastdns] 323 Cheshire, S. and M. Krochmal, "Multicast DNS", draft- 324 cheshire-dnsext-multicastdns-15 (work in progress), 325 December 2011. 327 [I-D.fleischhauer-ipv4-addr-saving] 328 Fleischhauer, K. and O. Bonness, "On demand IPv4 address 329 provisioning in Dual-Stack PPP deployment scenarios", 330 draft-fleischhauer-ipv4-addr-saving-03 (work in progress), 331 August 2012. 333 [I-D.wing-behave-http-ip-address-literals] 334 Wing, D., "Coping with IP Address Literals in HTTP URIs 335 with IPv6/IPv4 Translators", draft-wing-behave-http-ip- 336 address-literals-02 (work in progress), March 2010. 338 [I-D.yourtchenko-ipv6-disable-ipv4-proxyarp] 339 Yourtchenko, A. and O. Owen, "Disable "Proxy ARP for 340 Everything" on IPv4 link-local in the presence of IPv6 341 global address", draft-yourtchenko-ipv6-disable- 342 ipv4-proxyarp-00 (work in progress), May 2013. 344 [RFC2563] Troll, R., "DHCP Option to Disable Stateless Auto- 345 Configuration in IPv4 Clients", RFC 2563, May 1999. 347 [RFC3493] Gilligan, R., Thomson, S., Bound, J., McCann, J., and W. 348 Stevens, "Basic Socket Interface Extensions for IPv6", RFC 349 3493, February 2003. 351 [RFC3789] Nesser, P. and A. Bergstrom, "Introduction to the Survey 352 of IPv4 Addresses in Currently Deployed IETF Standards 353 Track and Experimental Documents", RFC 3789, June 2004. 355 [RFC3790] Mickles, C. and P. Nesser, "Survey of IPv4 Addresses in 356 Currently Deployed IETF Internet Area Standards Track and 357 Experimental Documents", RFC 3790, June 2004. 359 [RFC3791] Olvera, C. and P. Nesser, "Survey of IPv4 Addresses in 360 Currently Deployed IETF Routing Area Standards Track and 361 Experimental Documents", RFC 3791, June 2004. 363 [RFC3792] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 364 Currently Deployed IETF Security Area Standards Track and 365 Experimental Documents", RFC 3792, June 2004. 367 [RFC3793] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 368 Currently Deployed IETF Sub-IP Area Standards Track and 369 Experimental Documents", RFC 3793, June 2004. 371 [RFC3794] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 372 Currently Deployed IETF Transport Area Standards Track and 373 Experimental Documents", RFC 3794, June 2004. 375 [RFC3795] Sofia, R. and P. Nesser, "Survey of IPv4 Addresses in 376 Currently Deployed IETF Application Area Standards Track 377 and Experimental Documents", RFC 3795, June 2004. 379 [RFC3796] Nesser, P. and A. Bergstrom, "Survey of IPv4 Addresses in 380 Currently Deployed IETF Operations & Management Area 381 Standards Track and Experimental Documents", RFC 3796, 382 June 2004. 384 [RFC3927] Cheshire, S., Aboba, B., and E. Guttman, "Dynamic 385 Configuration of IPv4 Link-Local Addresses", RFC 3927, May 386 2005. 388 [RFC4795] Aboba, B., Thaler, D., and L. Esibov, "Link-local 389 Multicast Name Resolution (LLMNR)", RFC 4795, January 390 2007. 392 [RFC6555] Wing, D. and A. Yourtchenko, "Happy Eyeballs: Success with 393 Dual-Stack Hosts", RFC 6555, April 2012. 395 [Zeeb] "FreeBSD Snapshots without IPv4 support", 396 . 398 Appendix A. Solution Ideas 400 A.1. Remotely Disabling IPv4 402 A.1.1. Indicating that IPv4 connectivity is unavailable 404 One way to address these issues is to send a signal to a dual-stack 405 node that IPv4 connectivity is unavailable. Given that IPv4 shall be 406 off, the message must be delivered through IPv6. 408 A.1.2. Disabling IPv4 in the LAN 410 One way to address these issues is to send a signal to a dual-stack 411 node that auto-configuration of IPv4 addresses is undesirable, or 412 that direct IPv4 communication between nodes on the same link should 413 not take place. 415 A signalling protocol equivalent to the one from [RFC2563] but over 416 IPv6 is necessary, using either Router Advertisements or DHCPv6. 418 Furthermore, it could be useful to have L2 switches snoop this 419 signalling and automatically start filtering IPv4 traffic as a 420 consequence. 422 Finally, it could be useful to publish guidelines on how to safely 423 block IPv4 on an L2 switch. 425 A.2. Client Connection Establishment Behavior 427 Recommendations on client connection establishment behavior that 428 would facilitate IPv4 sunsetting would be appropriate. 430 A.3. Disabling IPv4 in Operating System and Applications 432 It would be useful for the IETF to provide guidelines to programmers 433 on how to avoid creating dependencies on IPv4, how to discover 434 existing dependencies, and how to eliminate them. Having programs 435 and operating systems that behave well in an IPv6-only environment is 436 a prerequisite for IPv4 sunsetting. 438 A.4. On-Demand Provisioning of IPv4 Addresses 440 No idea. 442 A.5. Managing Router Identifiers 444 Router IDs can be manually planned, possibly with some hierarchy or 445 design rule, or can be created automatically. A simple way of 446 automatic creation is to generate pseudo-random numbers, and one can 447 use another source of data such as the clock time at boot or 448 configuration time to provide additional entropy during the 449 generation of unique IDs. Another way is to hash an IPv6 address 450 down to a value as ID. The hash algorithm is supposed to be known 451 and the same across the domain. Since typically the number of 452 routers in a domain is far smaller than the value range of IDs, the 453 hashed IDs are hardly likely to conflict with each other, as long as 454 the hash algorithm is not designed too badly. It is necessary to be 455 able to override the automatically created value, and desirable if 456 the mechanism is provided by the system implementation. 458 If the ID is created from IPv6 address, e.g. by hashing from an IPv6 459 address, then naturally it has relationship with the address. If the 460 ID is created regardless of IP address, one way to build association 461 with IPv6 address is to embed the ID into an IPv6 address that is to 462 be configured on the router, e.g. use a /96 IPv6 prefix and append it 463 with a 32-bit long ID. One can also use some record keeping 464 mechanisms, e.g. text file, DNS or other provisioning system like 465 network management system to manage the IDs and mapping relations 466 with IPv6 addresses, though extra record keeping does introduce 467 additional work. 469 Authors' Addresses 471 Simon Perreault 472 Jive Communications 473 Quebec, QC 474 Canada 476 Email: sperreault@jive.com 478 Tina Tsou 479 Huawei Technologies (USA) 480 2330 Central Expressway 481 Santa Clara, CA 95050 482 USA 484 Phone: +1 408 330 4424 485 Email: tina.tsou.zouting@huawei.com 487 Cathy Zhou 488 Huawei Technologies 489 Huawei Industrial Base 490 Bantian, Shenzhen 491 China 493 Email: cathy.zhou@huawei.com 495 Peng Fan 496 China Mobile 497 32 Xuanwumen West Street 498 Beijing, Beijing 499 China 501 Email: fanp08@gmail.com